The invention relates to a process for oxidizing olefins to ketones by first hydrating an olefin to form a secondary alcohol and then dehydrogenating the secondary alcohol to the corresponding ketone.
Methods of producing ketones have become known which begin with the direct oxidation of an olefin with oxygen or air, the ketone being classed, as a rule, only as a coupling product or by-product of an olefin oxide. An example of this method is the preparation of propene oxide and acetone from propene and oxygen in which isopropanol acts as the oxygen transfer agent.
Other known processes for oxidizing olefins to ketone use for the oxygen transfer the exchange of the charges of cations in aqueous solution, without the formation of the epoxide of the olefin. These processes have the common disadvantage of a low transformation combined with a low yield of ketones, plus a considerable tendency towards corrosion of the equipment.
In the processes known for the preparation of ketones through the production of secondary alcohols from olefins followed by dehydrogenation of the secondary alcohols to ketones, extraction of the secondary alcohol for the dehydrogenation step is performed in an aqueous phase only. For example, in the processes performed with catalysts in the gaseous phase, the secondary alcohol is washed out of the vapor phase with water. In this process olefins are absorbed in dilute sulfuric acid with the formation of esters which have to be cleaved hydrolytically with water to form alcohols and more dilute sulfuric acid.
In the methods of the prior art for the direct hydration of olefins on fixedly disposed sulfonic acid type artificial resin exchangers, such as the commercially available Lewatit S 100(Farbenfabriken BAyer AG) and Dowex 50W (Rohms & Haas Co.,) which permit the achievement of satisfactory yields even at medium temperatures, an aqueous phase is likewise utilized to extract the secondary alcohols.